Method and plant for blending materials in bulk



Feb. 8, 1966 J. M. M. KELLY I METHOD AND PLANT FOR BLENDING MATERIALS INBULK Filed Aug. 3, 1964 '7 Sheets-Sheet 1 g N 4,; NW6.

4H'vrne g J. M. M. KELLY 3,233,877

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Feb. 8, 1966 7Sheets-Sheet 2 Filed Aug. 3, 1964 [N268 Nef/t J- Fla- 2h Attof'ngj theyMarie M J. M. M. KELLY 3,233,877

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Feb. 8, 1966 7Sheets-Sheet 5 Filed Aug. 5, 1964 I' v r W M 0 4 I m m a m VA .U WM 1(ls n e MU 30b Feb. 8, 1966 J. M. M. KELLY METHOD AND PLANT FOR BLENDINGMATERIALS IN BULK 7 Sheets-Sheet 4 Filed Aug. 3, 1964 PrllIIl mhm Iv MWM H. T K m. w 5 A T; e M 3 J; M. M. KELLY 3,233,877

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Feb. 8, 1966 '7Sheets-Sheet 5 Filed Aug. 3, 1964 3 3 q NKUZ Aflorne Feb. 8, 1966 J. M.M. KELLY 3,233,377

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Filed Aug. 3, 1964 '7Sheets-Sheet 6 Atfo rme Feb. 8, 1966 J. M. M. KELLY 3,233,877

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Filed Aug. 3, 1964 '7Sheets-Sheet 7 United States l atent O 3,233,877 METHOD AND PLANT FORBLENDING MATERIALS IN BULK Jacques Marie Michel Kelly, Paris, France,assignor to Societe des Mines de Fer de la Mouriere, Paris, France, acorporation of France Filed Aug. 3, 1964, Ser. No. 387,130 Claimspriority, application France, Aug. 13, 1960, 835,886; Jan. 13, 1961,849,635; Aug. 9, 1963, 944,371, Patent 1,272,184

21 Claims. (Cl. 259-180) This is a continuation-in-part of applicantsco-pending patent application Ser. No. 124,578, filed July 17, 1961,entitled Method and Plant for Rendering Homogeneous a Single DividedProduct of Non-Uniform Quality or a Mixture of Two or More DividedProducts Introduced in Fixed Proportions, now abandoned.

The present invention has for its main object a method of renderinghomogeneous a single divided product of non-uniform quality or a mixtureof two or more divided products introduced in fixed proportions. Thismethod is of the type wherein the homogeneousness of the desired mixtureis obtained or assisted by depositing the various constituents in heapsalong substantially parallel layers and by reclaiming the product alonglikewise parallel slices made at an angle to the lie of the depositedlayers.

When it is desired to render large tonnages homogeneous, it iscommonplace to resort to a method known in the metallurgical industry bythe name of bedding. This method consists in depositing the product tobe made homogeneous in a heap, along horizontal layers, and inreclaiming this heap along inclined slices intersecting the planes ofdeposit.

When it is desired to obtain mixtures by the bedding method, it isnecessary to have two storage areas: on one of these is the heap beingreclaimed, on the other the heap in the course of constitution. Thelarge amount of space needed and the fact that such discontinuousoperation entails variations of quality each time a heap is changed areboth drawbacks inherent to this method.

It has also been proposed to provide a pile of triangular cross section,the material to be blended being dispersed on the top of the pile inthin layers and reclaimed from the pile in thin layers at the base ofthe pile through a plurality of outlets.

If the different deposited layers were to remain parallel when thematerial goes down slowly and if the material was withdrawn at an equalrate by all the outlets, then the reclaimed layers would be of the samethickness along their entire length and would comprise an equal quantityof the materials of all deposited layers.

"Because of the great number of outlets, it will be diflicult to saywhich one exactly is involved, from the aspect of the variation of thesurface of the pile. If the correction is not made on the correctoutlet, there will be a further deformation of the layers which shouldremain parallel.

As the zone of deposit is just above the zone of withdrawl, thesevariations add indefinitely and even if it is possible to maintain thesurface of the bin with the right shape the layers inside will bedisturbed and the blending will not be satisfactory.

The present invention has for its object to overcome these drawbacks.

The method according to the invention is remarkable notably in that itcomprises the steps of forming a heap by continuously distributing at agiven rate said materials in substantially parallel layers, said layersbeing of different qualities, of simultaneously reclaiming at the sameice rate said materials along parallel cuts made at an angle to the lieof said layers, said heap thus retaining a constant mass and shape, oneof said two simultaneous steps being carried out along a slopeapproximating the angle of repose of said materials, whereby said heapis caused to move with a velocity related to the rate of distributingsaid materials in parallel layers.

Consequently the pile moves slowly.

It is easy to see that during this movement, the different paralleldeposited layers are not disturbed as the zone of reclaiming and'thezone of deposit are independent.

Moreover as the pile moves, the slightest variations that can occur inthe withdrawal of the material are not added indefinitely, and thelayers of reclaiming give very good samples of the pile.

According to one embodiment of the invention, the constituents of themixture to be obtained are deposited along parallel planes slightlyinclined relative to the horizontal, reclaiming being effected alongslices close to the vertical, or along the slope of fall down the sideof the heap, for example.

According to a further embodiment, the constituents of the mixture to beobtained are deposited along planes close to the vertical, correspondingto the slope of the fall down the side of the heap being constituted,reclaiming being effected along substantially horizontal slices.

According to a further embodiment, the component elements of the mixtureto be formed are disposed on a substantially even circular area so thatthe heap thus built up has a gradually decreasing cross-sectional area,the heap-forming layers being slightly inclined to the horizontal andthe material being picked up by mechanical means at the end of the heapwhich has the largest cross-sectional area along slices of which thelongest slope forms with the horizontal an angle approximating the angleof repose of the heap.

According to another characteristic feature, the component elements ofthe mixture are deposited onto the upper surface of the heap supportedby the aforesaid even circular area by means of a conveyor and/or aspout or the like describing with its outlet end a twofold alternatingmovement, one of circular configuration whereby this outlet end cansweep a sector limited by the two ends of the aforesaid circular heap,and the other in the radial direction for sweeping the entire length ofthe heap.

According to another characteristic feature of the invention, thematerials are picked up in the form of slices having a degree ofinclination approximating that of the aforesaid angle of repose, byusing any suitable pickup means, such as a harrow associated with anArchimedean screw, adapted to drop the picked up and homogenizedmaterials into an annular trough or the like disposed in the centralregion of said circular area.

According to a further characteristic feature of the invention, theaforesaid even circular area is defined by two cylindrcal coaxial wallsconstituting a kind of annular hopper of revolution of substantiallyrectangular cross-section and the aforesaid-heap when completed has agreater height at its outer periphery than centrally of said hopper, fora same radialcross-section.

It is a complementary feature of the invention that the aforesaid radialmovement of the conveyor means forming the heap of component elementstakes place at a variable speed depending on the distance existing between the place where the component elements are actually deposited andthe center of the aforesaid even circular area.

It will be readily understood that this method is independent of thenature of these componet elements since it is not based on the principleof a more or less uniform natural heap formation.

The invention also covers a plant for rendering homogeneous a singledivided product of non-uniform quality, or a mixture of two or moredivided products introduced in fixed proportions.

A plant according to the invention is notably remarkable in that itcomprises a single site adapted to receive a heap of said materials,distributing means for continuously distributing said materials ontosaid heap along substantially parallel layers, reclaiming means adaptedto continuously remove said materials from said heap along parallelslices at an angle to the lie of said layers, regulating devices toequalize the rate of material removal of said reclaiming means and therate of material delivery of said distributing means, arrangements tocontrol the motions of said distributing means and reclaiming meanswhereby one of said means is caused to move along a slope approximatingthe angle of repose of said materials.

In accordance with one embodiment, the site intended for the heapingoperation is a flat circular surface comprising, substantially in itsmiddle, a cavity forming a central funnel or conical hopper, the meansused for heaping the materials consisting in a belt conveyor,.a chute orsimilar device the end overhanging the heap of which describes analternating circular motion enabling it to sweep a sector bounded by thetwo edges of the heap formed over said circular surface, while saidreclaiming means consist of any convenient reclaiming device, such as anappliance with moving arms, a screw conveyor, a scraper and conveyor orthe like adapted to discharge into said central funnel the materialsreclaimed from the foot of the slope of fall down the heap.

According to a further embodiment, the site for heaping or stocking thematerials consists of an annular hopper of revolution of substantiallytriangular cross-section, say, comprising at its bottom, a circular slitthrough which the reclaiming can be performed, and the means used forthe heaping operation consist of a belt conveyor, a chute, or similardevice, the end overhanging the heap of which is possessed of acontinuous slow circular motion in step with the progression of thesloping face of the heap.

According to yet another embodiment, the plant comprises a prismatichopper of elongated rectangular plan form and preferably triangularcross-section, in which the constituents of the mixture to be obtainedare deposited in a heap, substantially over the slope of fall down thelatter at the end of said heap having the greatest crosssection, thereclaiming operation being carried out through the bottom of saidprismatic hopper.

According to another characteristic of this latter embodiment, whenprogression of the heap formed in the hopper has brought the foot of theslope of fall over which the deposits are made to the end of saidhopper, further deposits on the heap cease and the formation of a freshheap is begun at the opposite end of the hopper. The formation of thisnew heap is undertaken over an inclined surface which is preferably settransversely relative to the center-plane, of the hopper, said surfacehaving approximately the same inclination as the slope of fall down theheap progressing along the prismatic hopper.

According to another embodiment of the invention, the location forforming the heap is an even circular area comprising in a substantiallycentral position a cavity constituting an annular trough or the like,the heap-forming means consisting of a belt conveyor and a spout or thelike of which the outlet end overlying the heap performs a twofoldmovement, that is, a circular alternating movement on the one hand forsweeping a sector defined by the two ends of the heap formed on saidcircular area, and a radial alternating movement on the other hand, forsweeping the heap transversely, the pick-up means consisting of amechanical pick-u apparatus of any suitable iand known type adapted todrop into said central an nular trough the materials picked-up at thebase of saidi heap at the heap end having the major cross-section.

According to another feature characterizing this em-' bodiment, theaforesaid even circular area is defined by two vertical coaxialcylindrical walls forming an annular' hopper of revolution ofsubstantially rectangular crosssection, the aforesaid heap-forming meansoverlying saidl annular hopper.

It is a further feature of this invention and a specific: form ofembodiment thereof that the aforesaid heap-- forming means consist .of amovable bridge structure: to which an alternating circular motion can beimpressed; for sweeping therewith asector rotating very slowly; which isdefined by the two circular ends of the heap formed thereunder, a framebearing on said bridge structure and receiving a radial alternatingmotion, a beltor like conveyor being provided on said frame fordelivering the component elements of the heap being formed to a spout orthe like provided at the outlet end of said frame and overlying saidheap.

Yet further characteristics of the invention will become apparent fromthe following description in which reference is had to the accompanyingdrawings given by way of example only and not limitation, and in which:

FIGURE 1 is a schematic illustration of the manner of heaping andreclaiming a product according to the method known as bedding.

FIGURE 2 is a highly diagrammatic illustration of the development of aheap as obtained according to the invention, the constituents of themixture to be obtained being deposited along parallel planes slightlyinclined to) the horizontal, and reclaiming being accomplished along:slices to the vertical, made along the slope of fall dowm the heap.

FIGURE 3 is a schematic illustration of the development of a differentheap obtained in accordance with the invention, the constituents of themixture to be ob-- tained being deposit-ed along planes close to thevertical, or along the slope of fall down the heap, for example,. andreclaiming being accomplished along substantially horizontal slices.

FIGURE 4 is a plan view of a mixing plant according; to the invention,comprising a flat circular area over: which the heap may be formed.

FIGURE 5 is a cross-section through the line VV' in FIGURE '4.

FIGURE 6 is a plan view of a mixing plant according to the invention,comprising an annular hopper for the heaping operation. 7

FIGURE 7 is a cross-section through the line VIIVII in FIGURE 6.

FIGURE 8 is a cross sectional view of a plant slightly different fromthe one shown in FIGURES 6 and '7.

FIGURE 9 is a highly diagrammatic longitudinal section through thevertical centre-plane of a mixing plant comprisinga prismatic hopper.

FIGURES l0 and 11 explain schematically the manner of progression of aheap in the installationshown in FIGURE'Q.

FIGURE 12 shows diagrammatically the manner inv which the materials areheaped and picked up according, to another method of this invention.

FIGURE 13 shows in plane view from above the complete arrangement ofFIG. 12 according to the present invention.

FIGURE 14 is a diagram showing the contour lines of the heap ofmaterials which is formed as illustrated in FIGURE 13.

FIGURE 15 is an elevational and sectional view with parts broken away.showing a complete installation con-.

structed according to the present invention, and

FIGURE 16 is a basic diagram showing in Cartesian co-ordinates thevariable velocity of the spout delivering the materials to the heap as afunction of the radial distance between the said spout and the center ofthe mixingplant.

The invention consists essentially in substituting for mixing methodsutilizing purely static heaps and known as bedding methods, a method theprinciple of which is derived from said bedding methods but which causesthe heap to progress along the stocking area.

Since the progression of the heap takes place on a single site, it ispossible to perform the heaping and the reclaiming operations incontinuous manner, a thing it is impossible to achieve otherwise.

Referring now to FIGURE 1, the reference numeral 1 designates a heapformed by the bedding method referred to previously. The figure showsthe formation on this heap 1 of successive beds deposited substantiallyhorizontally. The reference letters dd designate one of the layers inthis heap. Once the heap has been formed with the number and thicknessof layers needed to obtain the desired mixture when reclaiming, thelatter is performed along slices denoted by ee' in FIGURE 1. Theseslices or reclaimings are effected, say, over the slope of fall down theheap until the latter is completely exhausted. In such cases the heapmay be said to be consumed in sitju.

FIGURE 2 shows a heap 2 obtained by the method according to theinvention. On this heap 2, the successively deposited parallel layerssuch as dd are slightly inclined to the horizontal, as a result of whichsaid heap 2 has a maximum section in the vertical plane that passesthrough the point 4, which is the summit of the slope of fall.

Reclaiming is accomplished along slices ee over the slope of fall downthe heap 2, and this reclaiming can be achieved by excavating at thefoot 5 of said slope of fall.

In contradistinction to what occurred in the case of the heap 1 inFIGURE 1, the heap 2 need not disappear in situ. For this, it willsuffice to continue to supply makeup materials along the deposit layersdd to compensate for the volume reclaimed at ee. An examination of FIG-URE 2 will show that the heap 2 will not remain static, but that it willbe displaced in the direction of the arrow F2. Furthermore, there is noreason why the heap should not be formed along a near-closed curve withthe point 5 at the base of the reclaiming slope close to the point 7where the heap tapers away to its minimum section. This is in fact thearrangement adopted in the installation that will be describedhereinbel-ow, such installation offering the advantage of being capableof continuous operation over a relatively small piece of ground.

The heap 3, which is likewise produced in accordance with the invention,is established by depositing the constituents of the desired mixturealong successive beds which form layers dd substantially parallel to theslope of the heap, between the points 8 and 9. Reclaiming is eifectedalong substantially horizontal slices ee at the base 8-40 of the heap.

Like the heap 2, the heap 3 can be maintained in continuous operationprovided that the material reclaimed at 3-1$ is made up by furtherheaping at 89. The heap 3 will then progress in the direction of thearrow F3. As will be seen from the embodiments of installationsdescribed later, it is obviously possible to cause the heap to be formedover a near closed curve with the points 8 and 10 in close proximity toeach other, thereby ensuring a circular progression of the heap over arelatively small site.

FIGURES 4 and 5 show a plant designed for performing the methodaccording to the invention.

The heap 2 is formed over a substantially circular area 12. Theconstituents of the mixture to be heaped are conveyed to the mixingplant by a conveyor 13 which spills them in proximity to the end 14 of aconveyor 15 adapted to slew about a vertical axis 16 to enable its end17 to describe a circular path above the stocking site 12.

In the centre of said stocking site 12 is a conical 6 hopper or funnel18, the substantially circular upper edge of which lies in the plane ofthe fiat stocking site 12.

A reclaiming appliance 19 is disposed radially above the site 12. Thisappliance is possessed of rotating motion about the axis 16 and its typewill depend on the kind of material to be handled, examples of such anappliance being those equipped with mobile arms, conveyor screws,scrapers, conveyors and the like.

The manner of operation of the plant described hereinabove is extremelysimple. The products to be mixed are brounght up by the conveyor 13 anddistributed over the heap by the conveyor 15, which is possessed of asufficiently rapid oscillating motion about the axis 16 to ensure thatthe layers of product deposited over the heap are not too thick. Theamplitude of this oscillating motion will be close to a complete circle,and examination of the plan view in FIGURE 4 will show that travel ofthe conveyor 15 takes place from the point 4 to the point 7, and viceversa.

It will be appreciated that it will be necessary for the heap to advancein the direction of the arrow F2 as it is reduced from the base of itsslope of fall (the summit of which is the point 4) by the reclaimingappliance 19, and to this end the rate of travel of said reclaimingappliance 19 is synchronized with the shift of the sector defined by theangle 4, 16, 7.

The mixed and homogeneous product introduced by the reclaiming appliance1% into the funnel-shaped hopper 18 is extracted and conveyed to itsutilization point by a conveyor 20.

The plant shown in FIGURES 6 and 7 comprises, by way of storage meansfor the heap 3, an annular shaped hopper forming a body of revolutionabout a vertical axis 22. The products to be mixed are introduced intosaid hopper 21 by a conveyor 23 which is pivotable about the axis 22 andthe end 24 which describes a circle the centre of which is located onthe axis 22, above the annular hopper 21. At the base of hopper 21, thecrosssection of which is substantially triangular, is a slit 26 throughwhich can be extracted the products accumulated in the hopper 21. Thisextraction can be facilitated by scrapers (not shown); after passagethrough said slit 26, the product drops into a circular conveyor 27comprising an endless chain of contiguous buckets designed to tip theircontents into the hopper 28 which feeds a conveyor 29 the purpose ofwhich is to evacuate the mixed and homogeneous product to theutilization point.

The manner of operation of the plant illustrated in FIGURES 6 and 7 isas follows: the constituents of the mixture are carried to the conveyor23 by the conveyor 25. They then drop onto the heap 3 at the point 9 anddistribute themselves through the hopper 21, over the slope of fall downthe heap and between the points 9 and 8, for example. Reclaiming takesplace through the slit 26 provided at the bottom of the hopper 21.

If an examination he made of the plan view of the plant shown in FIGURE6, it will be appreciated that the heap 3 will advance in the directionof the arrow F3, and that the displacement of the heap and that of theconveyor 23 which distributes the mixture constituents will berigorously identical. It is manifest that proper adjustment of such aplant requires that the output of product from the conveyor 23 and thatfrom the slit 26 be the same.

FIGURE 8 shows an alternative installation to that just described. Thisis much simpler in design, in the sense that it dispenses with thecircular bucket conveyor and that the slit 26 discharges directly into afunnelshaped hopper 36 into which the product excavated by one or morescrapers 31 from the slit 26 drops before being evacuated by a conveyor32. Another point which distinguishes the plant in FIGURE 8 from that inFIG- URES 6 and 7 is the fact that, in the case of the former, the heap3 is fed through a chute 33 supplied with mixture constituents by aconveyor 34.

From the .description given above it will have been realized that theplant shown in FIGURES 4 and 5 corresponds to a heaping and reclaimingas schematically illustrated in FIGURE 2, whereas the installations ofFIGURES 6, 7 and 8 correspond to a heaping and reclaiming of the formschematically illustrated in FIGURE 3.

To permit proper placement of the two circular forms of plant describedhereinbefore, it is necessary to provide a site which is likewisecircular or square, and of relatively large size. On the other hand, forreasons of availability between two existing installations, forinstance, it may be found convenient to use a site of elongated shapeand simultaneously provide suitable mechanical handling means such asconveyors or the like designed to operate in a straight line.

The installation illustrated schematically in FIGURE 9 is designed to beset up on a site of elongated shape. On this figure is shown a heap 111obtained by depositing, as 112, the constituents of the mixture to beobtained, the latter sliding down the face 112-113 of the heap. Thisheap 111 is formed in a hopper 114 of substantially triangular section,the base of which comprises a horizontal slit through which travels anextraction device schematically illustrated at 115. 'This device maytake the form, say, of a scraper possessed of to-and-fro motion betweenthe ends 116 and 117 of the base of the hopper 114. At its end 117, saidhopper 114 is bounded by an inclined plane 117-118 having asubstantially identical slope to that of the face 112-113 of the heap.The utility of this inclined surface 117-118 will become apparent fromthe description given later of the manner of operation of theinstallation.

Beneath the slit 116-117 through which travels the scraper 115 isarranged a straight conveyor belt 119 which conveys the mixedconstituents extracted from the hopper 114 by the scraper 115 towardsthe utilization point.

A belt conveyor 120, preferably of the same type as the conveyor 119, isprovided above the hopper 114, preferably in the vertical centre-planethereof. A means of spilling the products transported by the conveyor12) onto the heap 111 is illustrated schematically at 121, and thisdevice 121 may be a spilling crab, for example, which travels in such away as to ensure that the deposits made on the heap 111 effectively takeplace over the slope of fall 112-113 down said heap 111. In other words,the spilling-crab 121 travels in the direction of the arrow F, at thesame speed as the heap 111 which it overhangs. The conveyor 120 issupplied by a device 122 (an intermediate hopper for example), intowhich are discharged, by a suitable conveyor such as a travelling chute,a noria hoist, a belt conveyor or the like, the products used to make upthe mixture.

Two conditions must be fulfilled for the mixture to be effectedcorrectly; the weight of deposited material must besubstantially equalat all times to that of the reclaimed material, secondly, the crab 121must travel above the heap 111 at a speed which is directly proportionalto the weight of material conveyed by the belt 120.

As an example, the rate of travel of the crab 121 may be controlled byindications given by a weigher A arranged on the conveyor 120, and theweight of material admitted through the hopper 122 controlled by meansof a weigher B on the conveyor 119.

This installation may be controlled manually, semiautomatically or fullyautomatically. In the case of manual operation, an operator would haveno difiiculty in regulating the quantity admitted through the hopper 122in such a way as to ensure that the weights integrated by the weighers Aand B are as nearly equal as possible at all times.

Assuming the various conditions of operation described above to havebeen fulfilled, the manner of functioning of the installation shown inFIGURES 9 to 11 is as follows:

Referring to FIGURE 9, it will be appreciated that the heap 111 and thecrab 121 which feeds it will both advance in the direction of the arrowF, until the foot 113 of the slope 112-113 reaches the end 116 of thehopper 114. At this end 116, the hopper may indifferently be bounded bya vertical wall or be slightly inclined or even be open. Indeed, as soonas the foot 113 of the slope of fall down the heap reaches the point116, deposits on the heap 111 are made to cease and the spilling crab121 is quickly brought. above the point 118 on the inclined plane117-118 which bounds the prismatic hopper 114.

FIGURE 10 is a diagrammatic illustration of the same installationshortly after the crab 121 has begun to discharge the product over theface 117-118. The heap which, when the spilling crab 121 ceases todischarge, has a profile as shown in broken lines in FIGURE 10, hadbegun to discharge through the slit at the bottom of the hopper 114. Inthe intervening time, under the action of the scraper 115, a tonnageidentical to that discharged over the inclined surface 117-118 by thespilling-crab 121 has been discharged on to the belt 119.

If reference be now had to FIGURE 11, it will be seen that a heap 111ais being formed by the discharge of mixture constituents by the spillingcrab 121 over the face 112a-113a. While this heap 111a is being formedand progresses in the direction F, the simultaneous gradualdisappearance, in situ, of the heap 111 on the left of FIGURE 11 may beobserved.

Since the tonnage deposited by the spilling-crab 121 is the same as thatremoved by the scraper 115, a constant tonnage is at all times availablein the hopper 114, and this tonnage may take the form of a single heap(FIGURE 9) or that of two heaps, of which one, 111a is in the course offormation and the other, 111, in the course of disappearance (FIGURES 10and 11). If it is assumed that the areas of the hatched sections inFIGURES 9 to 11 are substantially proportional to the tonnages of theheaps they respectively represent schematicaily, then it will be seenthat the single heap 111 of FIGURE 9 can easily be reconstituted fromthe heaps 111a and 111 of FIGURE 11. This can easily be demonstrated byimagining that the hatched triangle (the is joined to the shorter of theparallel sides of the trapezium 111a, as at ab'c.

In this latter embodiment, in other words, a to-and-fro motion withinthe hopper 114 has been substituted for the circular motion of the heapdescribed in previous embodiments.

In the description given hereinabove it has been assumed that theinclined plane 117-118 has substantially the same slope as the face112-113 of the heap 111. Clearly, the face 117-118 does not behave inrigorously the same way as the face 112-113 when the spilling crab 121discharges its deposits. It is preferable for the face 117-118 to behaveas much as possible like the natural slope of fall. down the heap. Forthis reason, it will be necessary to vary thoroughly study, empiricallyfor example, the shape and nature of said face 117-113. The latter neednot necessarily be plane and may embody various irregularities such asripples, trenches or channels, which may be directed longitudinally ortransversely.

More particularly, in FIGURES 2 and 4, there has been described aprocess wherein a substantially circular heap is formed by depositingthe component elements of the mixture to be formed on a substantiallyeven area. To this end a conveyor pours along a circular arc thecomponent elements of the heap, the latter widening as it is broughtdown. At the end where the heap has its maximum cross-sectional area thecomponent elements are picked up at the bottom or base of the heap bysimply digging this heap which falls or slips down gradually. Thematerials are picked up by slices substantially par- 9 allel to thelongest slope, or angle of repose of the heap.

Although this method and similar methods, such as the ones disclosedwith reference to FIGURES 3 and 6 thereof, are definitely suited forhandling dry ores having a uniform grain size, they are subject tovarious drawbacks when handling ores of very irregular grain size and/orhaving a variable moisture content.

In fact, under these conditions a certain segregation in the slices orlayers deposited in succession along the angle of repose or heap slopeis likely to take place. An irregular pick-up rate of the productsdeposited on the heap may also be expected. These two irregularities mayresult in a distortion of the parallelism of the slices deposited ontoand picked up from the heap, and therefore the picked-up ore may nothave exactly the average quality of the products previously delivered toform the heap.

To avoid these drawbacks the present embodiment provides, as shown inFIGURE 12, a method of depositing the component elements of the heap inthe form of layers dd, the lines of longest slope of these slicesforming with the horizontal a moderate angle inferior to the angle ofrepose of the heap. Under these conditions any segregation orirregularity in the successive layers thus deposited are definitelyprecluded.

On the other hand, the component elements of the heap are picked up inthe form of slices era of which the line of longest slope forms with thehorizontal an angle inferior to the angle of repose of the heap. Also inthis case any possibility of segregation or irregularity in these slicesis safely avoided.

The heap illustrated in FIGURE 12 advances substantially like the onedescribed with reference to FIGURE 2. When the slices 2e are removed insuccession by using adequate mechanical pick-up means as will beexplained presently the heap 200 advances to the right, in the directionof the arrow F4. Since this heap is formed along a substantiallycircular curve it will move around as the component elements aredeposited and picked up.

In FIGURE 13 of the attached drawings this circular heap is shown asviewed from above. In this example the heap is built up inside theannular space formed by two concentric circular walls 201 and 202. Themanner in which this two-walled hopper is constructed will be consideredmore in detail presently. FIGURE 13 shows diagrammatically the heap 203of materials deposited according to the method illustrated in FIGURE 12.

The contour lines of FIGURE 14 show the shape assumed by the suruface ofthe heap tthus formed,

FIGURE 13 also shows the mechanical means 204 and 205 provided forpicking up the products or materials from the heap. The device 204-consists for example of a studded-harrow, and the device 205 associatedtherewith consists of an Archimedean screw or like device adapted topick up the materials swept by the harrow 204 towards the bottom of theheap, that is, to their discharge place. In this figure there is alsoshown a movable bridge structure 206 adapted to revolve about a pivot(not shown) having its axis coincident with the center of the hopper andbearing on the other hand by means of casters, wheels or bearings 207 onthe substantially flat rail-forming top edge of the outer circular wall281. Inside this movable bridge structure 206 a movable frame 206a ismounted for longitudinal motion and carries a belt conveyor 209 adaptedto feed a pouring spout 208.

A heap of the type shown diagrammatically in FIG- URE 12 is easilyformed by means of this arrangement.

The component elements of the mixture are fed from the center 0 to theconveyor 209 and according to the variable position of the rotatablymovable bridge structure 206 and of the radially movable pouring spout208 the component elements of the mixture to be for-med are poured ontosuch other selected location of the heap 2113.

FIGURE 15 shows more in detail a typical arrange ment for carrying outthe method set forth hereinabove.

In this FIGURE 15 there is illustrated inradial section with partsbroken away an annular supporting area or bed 210 disposed between twovertical cylindrical coaxial walls, i.e. an outer wall 211 and an innerwall 212 constituting a hopper 213 formed in the resulting annularspace. The area 210 and walls 211, 212-, may consist for example ofreinforced concrete or like material. External pillars 214 and a centralcolumn 215 support the construction. Of course, the area 210 may alsoand preferably be formed directly on the ground. A stationary bridge 216of trussed beams or concrete construction overlies the complete unit andis supported by pillars or like elements 217. These pillars or likeelements 217 may have one or more portions merged into some of theaforesaid pillars 214 reinforced to this end.

Having thus described the main structure of the apparatus the means forforming the heap of ore or like material comprise a feed conveyor 218mounted on the stationary bridge 216 and adapted to discharge the ore orlike material into a spout 219. A vibrating distributor 220 is providedfor assisting in delivering the material to a conveyor 22-1 mounted on amovable bridge structure 222. This movable bridge structure 222 issupported in the central portion of the assembly by a pintle 223supported by and revolving in a cavity 224 provided to this end in thecentral column 215. The opposite ends of this movable bridge structureare adapted to roll, by means of suitable rolls, wheels or the like 225,on the upper flat face 226 constituting the upper edge of the outer wall211. These rolls or wheels 225 may consist for example of a pair oftire-mounted wheels, one wheel being driven from a power unit through areducing gearing (not shown) adapted to drive the outerends of bridgestructure 222 at the desired and suitable speed. This bridge structure222 is adapted, of course, to pivot about the axis of the hopper 213formed by the concentric coaxial vertical walls 211, 212. Control meansshown only in diagrammatic form are provided and comprise a limit switchand a reversing switch 227 actuated by stop members carried by a movableannulus 228 so as to impart to the bridge structure 222 an alternatingcircular motion corresponding to the one described in the presentinvention. The movable annulus 228 revolves at a relatively slow ratecorresponding to an angular speed proportional to the mass of materialintroduced into the apparatus. Thus, a heap having a contoursubstantially as shown by the reference letter T in FIGURE 15 is formed.

The conveyor 221 is mounted on the movable bridge structure 222 by meansof a movable frame 229 to which a radial reciprocating motion isimparted so that the products being handled fall into a spout of whichthe two end positions are shown at 230 in thick lines and at 231 inbroken lines, respectively. Of course, the radial reciprocatingmovements of the frame 229 are produced by means of a power unit andreduction gearing of the variable-speed type driving a chain or liketransmission member. To simplify the drawing the power unit, reductiongearing and chain, on the one hand, and the means enabling the frame229; to roll on the bridge structure 222 are not shown.

The ore or like material to be handled is picked up by mechanical meanssuch as a harrow (not shown) adapted to bear on a pair of circular rails233, 234, embedded on the walls 211, 212 and by an ore loading apparatus235 consisting for instance of an Arcln'medean screw or the like. Thisloader 235 bears in turn on a rail 236 and on a bar or like member 237permitting its rotation about the central column 215. Of course, thisloader 235 is pushed towards the heap and driven in a mannercorresponding substantially to the one described with reference toFIGURES 4 and 5 thereof. The ore picked up by these means is dischargedinto an annular space 238. In this annular space 238 doctors or likeblades revolving in said space under the control of adequate rollerspick up the ore and deliver same toan orifice 240 formed through thebottom of the aforesaid annular space 238 onto a vibrating distributor241 and a discharge conveyor 242.

The arrangement described hereinabove is characterized by otheradvantageous constructional features such as for instance the provisionof ring collectors 243 for supplying current to the loader motor, acentral ladder 244 in the hollow central column 215 to permit theregular inspection of various parts of the mechanism, notably thebearing of pintle 223 and the electrical contacts 245 provided at thebottom of pintle 223 for energizing the motors of the movable bridgestructure 222 and of the conveyor 221.

Of course, as in the construction exemplified in the present invention,an automatic integrating sca-le (not shown) is provided on the conveyor218 delivering the material to the heap, this scale being adapted toadjust the various creep rates of the heap, since the ends of this heapconstantly move along a circular path as a consequence of the operationof the above-described devices 227 and 228.

To obtain a heap built up according to the contour lines shown in FIGURE14 it is necessary toimpart to the pouring spout 230 carried by the endof the movable conveyor 221 a variable-speed radial reciprocatingmotion.

In FIGURE 14, the reference numerals 0, 0.5, 1, 1.5, 2 l0, designate theheight (for example in feet) of the contour line of the heap withrespect to the bottom 210 (zero level) of the hopper.

More particularly, the rate of this reciprocating motion may beinversely proportional to the square of the distance measured from thespout 230 to the axis of the material-handling plant. This is clearlyshown in FIGURE 16.

In the diagram of this figure the distances from the pouring spout 23%to the axis of the plant are plotted in abccissae against the rate ofreciprocating motion of frame 229 in ordinates. On the other hand, thecurve C showing the momentary speed of spout 23) is traced. Moreparticularly it will be seen that when the spout reaches the centralwall 212 the frame speed is maximum and corresponds to the ordinateV212. On the other hand, when the spout 230 reaches the outer wall 211,the frame speed is minimum and corresponds to the ordinate V2.11.

Of course, at these endmost points the movements are stopped andreversed. To obtain this law of variation of the frame speed a cam (notshown) may be used, this cam consisting for example of a plate elementcarried by the frame 229 and adapted, according to the sucoessivepositions occupied by the frame on the bridge structure 222, to actuatefor instance, through a rollers and levers system a variable-voltagedevice. If desired, this variable-voltage device'rnay be of thethyratron type adapted to control the energization of a direct-currentmotor impressing the aforesaid radial reciprocating motion to the frame229. Thus, the heap will constantly assume the configuration illustratedin FIGURE 14 and any risk of crumbling or falling in of the heap, andtherefore any risk of segregation, are definitely precluded.

Various other features of this invention may be used in practice. Thus,more particularly, the short reach of conveyor 221 which will operateunder relatively severe conditions will be preferably of relativelygreat width. In fact, the greater belt width will make it possible tooperate the conveyor at a relatively low linear speed and therefore toincrease the useful life of the belt for a transported load.

On the other hand, as the 'ore is usually introduced and deliveredbatchwise to the heap, in order to avoid a non-uniform distribution andthe detrimental introduction of similar qualities simultaneously, itwill be well to use properly selected mean time periods for introducingthe unitary batches, adequate oscillation frequencies of the movablebridge structure in rotation, and of the frame structure in radialtranslation, so that these time factors be in prime ratio to oneanother. Thus, if for instance during the beginning of the oreintroduction the ore displays such or such special characteristic, theore thus deposited will be distributed uniformly over the heap and willnot interfere with the homogeneity of the component elements picked uptherefrom.

The choice to be made between the different types of installationdescribed hereinbefore, or between others of a similar type, will bemade according to the characteristics of the constituents to be mixedand of the mixture to be obtained, due allowance being made for thetonnages to be processed, the peak output of the plant, the sieve sizeof the constituents, and so on.

Installations that operate an annular hopper instead of a flat stockingsurface offer the advantage of having smaller overall dimensions. On theother hand, installations that make use of fiat surfaces forconstitution of the heaps would appear to be better suited when thesieve size of the products covers a wide range and when a tendencytowards physical segregation is to be feared.

By virtue of their faculty for continuous operation, all the types ofmixer designed in accordance with the present invention lend themselvesto automatic control.

With installations according to the invention, there is no further needto fear quality fluctuation-s such as those which arise when operationis intermittent due to changes from one heap to another, and it ispossible to still further improve the functional characteristics of suchinstallations by recycling part of the product emerging from the plant,a feature which can be incorporated without increasing the overall sizeof the plant.

The field of application of plant according to the invention is a verywide one. Such plant can be used with advantage in the metal, glass,cement and other industries. Embodiments built along the lines of thoseshown in FIG- URES 3 and 7, which permit the obtainment of plants ofrelatively smaller size, canfiud application in the pharmaceutical,chemical, food and similar industries.

It is to be clearly understood that the present invention is by no meanslimited to the foregoing embodiments, which were described andillustrated by way of example only.

What I claim is:

1. A method of blending materials in bulk comprising the steps offorming a heap by continuously distributing at a given rate saidmaterials in substantially parallel layers, said layers being ofdifferent qualities, and of simultaneously reclaiming at the same ratesaid materials along parallel cuts made at an angle to the lie of saidlayers, said heap thus retaining a constant mass andshape, one of saidtwo simultaneous steps being carried out along a slope approximating theangle of repose of said materials, whereby said heap is caused to movewith a velocity related to the rate of distributing said materials inparallel layers.

2. A method of blending materials in bulk comprising the steps ofcontinuously distributing at a given rate said materials on a heap insubstantially parallel layers slightly inclined to the horizontal, saidlayers being of different qualities, and of simultaneously reclaimingsaid materials at the same given rate along a slope approximating theangle of repose of said materials, said heap thus retaining a constantmass and shape and moving with a velocity depending on said distributingrate.

3. A method according to claim 2, wherein said materials are distributedaccording to a substantially circular heap of uniformly decreasingcross-section from the top of said slope.

4. A method of blending materials in bulk comprising the steps ofcontinuously distributing at a given rate said materials on a heap insubstantially parallel layers, said layers being of different qualities,along a slope approximating the angle of repose of said materials, andof simultaneously reclaiming at the same rate said materials insubstantially parallel horizontal layers at the bottom of said heap,said heap thus retaining a constant mass and shape and moving with avelocity depending on said reclaiming rate.

5. A method of blending materials in bulk comprising the steps ofcontinuously distributing at a given rate said materials on a heap insubstantially parallel layers, said layers being of different qualities,the component elements of the mixture to be formed being deposited ontoa substantially even circular area so that the heap thus built up has agradually decreasing cross-sectional area, the heap-forming layers beingmoderately inclined to the horizontal, and of simultaneously reclaimingat the same rate said materials, the mixture being picked up bymechanical means at the end of said heap Where the heap has its maximumcross-sectional area by slices of which the longest slope forms with thehorizontal an angle slightly inferior to the angle of repose of theheap, whereby saidheap is caused to move with a velocity related to therate of distributing said materials in parallel layers.

6. A method according to claim wherein the component elements of themixture are deposited onto the upper surface of the heap by conveyormeans describing with its discharge end a path corresponding to a doublereciprocating movement, that is, on the one hand, a circularreciprocating movement enabling said discharge end to sweep the sectorlimited by the two ends of said circular heap, and on the other hand aradial reciprocating movement enabling said discharge end to sweep theentire width of said heap.

7. A method according to claim 6 wherein said conveyor means includesspout means the pouring end of which describes said path and performssaid circular and said radial movements.

8. A method according to claim 6 wherein the materials are picked up byslices having a degree of inclination approximating the aforesaid angleof repose, by using pick-up means adapted to drop the picked-up andhemogenized material into an annular or similar trough disposed in thecentral region of said circular area.

9. A method according to claim 8 wherein said pick-up means includesbarrow means associated with an Archimedean screw.

10. A method according to claim 6 wherein the rate of said radialmovement is variable as a function of the distance from the locationwhere these elements are deposited to the centre of said even circulararea.

11. A method according to claim 10 wherein the materials are depositedinto an annular hopper constituted by two coaxial cylindrical wallsbuilt on said circular area and the radial velocity of said dischargeend is proportional to the inverse of the square of the distance fromthe location where the component elements are deposited to the centre ofsaid annular hopper.

12. A method according to claim 6 wherein the radial and circularoscillation periods of said discharge end are in a given relationship.

13. A method according to claim 12 wherein the component elements of themixture are introduced batchwise, the mean duration of the introductiontime of said batches, and the periods of said circular and said radialoscillations being in prime ratio to one another.

14. A plant for blending materials in bulk comprising a single siteadapted to receive a heap of said materials, distributing means forcontinuously distributing said materials onto said heap alongsubstantially parallel layers and reclaiming means adapted tocontinuously remove said materials from said heap along parallel slicesat an angle to the lie of said layers, said distributing means, togetherwith said reclaiming means, being effective to 14 cause a continuousresulting progression of said heap along the site.

15. A plant for blending materials in bulk comprising a fiat annulararea, a cavity in the center of said area forming a delivery hopper,distributing means reciprocally and angularly swingable between twoangular end positions above said area about a vertical axis passingthrough the center of said area for conveying said materials onto saidarea to form a heap thereon, deposits being made along substantiallyparallel layers between said two end positions, and reclaiming meansradially disposed with respect to said vertical axis to be advanced intosaid heap along an exposed face slope determined by the angle of reposeof said materials and to discharge said materials into said centralcavity, said distributing means being adapted to continuous angularshifting of both of said end positions in the same direction and by thesame angle as that of advancement of said reclaiming means, thus causinga progression of the heap onto said area.

16. A plant for blending materials in bulk comprising an annular hopperof revolution of substantially triangular cross-section, distributingmeans rotatable about the vertical axis of said hopper for depositingsaid materials into said hopper to form a heap therein, deposits beingmade along substantially parallel layers over an exposed face slope ofsaid heap determined by the angle of repose of said materials, andreclaiming means comprising a circular slit at the bottom of said hopperand shifting scraper means in said slit to control the reclaiming ofsaid materials out of said hopper so that the rate of reclaiming saidmaterials is equal to the distributing rate of same, said distributingmeans being adapted to perform a slow continuous shifting, thus allowinga circular progression of the heap into said hopper.

17. A plant for blending materials in bulk comprising a prismatic hopperof elongated rectangular shape and substantially triangularcross-section, distributing means longitudinally movable above saidhopper for depositing said materials into said hopper to form a heaptherein, deposits being made along substantially parallel layers over anexposed face slope of said heap determined by the angle of repose ofsaid materials, and reclaiming means comprising a longitudinal slit atthe bottom of said hopper and shifting scraper means in said slit tocontrol the reclaiming of said materials out of said hopper so that therate of reclaiming said materials equalizes the distributing rate ofsame, said distributing means being adapted to perform a slow continuousmotion, thus allowing a longitudinal progression of the heap into saidhopper.

18. A plant as claimed in claim 17 wherein said prismatic hoppercomprises an inclined end wall having a slope approximating the angle ofrepose of said heap face.

19. A plant for blending materials in bulk comprising an even circulararea for building up the heap of said materials, said circular areacomprising a cavity constituting an annular trough substantially locatedin the center of said circular area, the heap-building means comprisinga first conveyor mounted on a stationary part of the plant overlyingsaid area, axially located spout means fed by said first conveyor andfeeding a second conveyor, a frame carrying said second conveyor, abridge structure onto which said frame is mounted diametrically withrespect to said area, second spout means carried by said frame and fedby said second conveyor, said bridge structure being adapted to receivea circular reciprocating motion, the reversing of said motion beingordered by two stop members carried by an annulus and contacted by saidbridge structure, said annulus being adapted to revolve at a slow ratearound its axis which passes through the center of said area, and saidframe being adapted to receive a radial reciprocating motion so thatsaid second spout means may describe a twofold movement, on the one handa circular reciprocating movement for sweeping the sector limited by thetwo ends of the heap being formed on said even circular area, and on theother hand a radial reciprocating movement for sweeping the heaptransversely, the means for picking up the mixture from the heapconsisting on the other hand of a mechanical pick-up device of anysuitable type to drop into said central annular trough the materialspicked up at the base of said heap, at the heap end having the greatestcrosssectional area, said heapbeing thus caused to move with a velocityrelated to the rate of picking up said mixture by the pick-up device.

29. A plant according to claim 19 wherein the aforesaid even circulararea is limited by two vertical coaxial cylindrical walls -forming anannular hopper of revolution of substantially rectangular cross-section,said heapforming means overlying said annular hopper.

References Cited by the Examiner UNITED STATES PATENTS 2,385,494 9/1945Boynton 2 5. 9180 WALTER A. SCHEEL, Primary Examiner.

JOHN M. BELL, Assistant Examiner.

1. A METHOD OF BLENDING MATERIALS IN BULKS COMPRISING THE STEPS OFFORMING A HEAP BY CONTINUOUSLY DISTRIBUTING AT A GIVEN RATE SAIDMATERIALS IN SUBSTANTIALLY PARALLEL LAYERS, SAID LAYERS BEING OFDIFFERENT QUALITIES, AND OF SIMULTANEOUSLY RECLAIMING AT THE SAME RATESAID MATERIALS ALONG PARALLEL CUTS MADE AT AN ANGLE TO THE LIE OF SAIDLAYERS, SAID HEAP THUS RETAINING A CONSTANT MASS AND SHAPE,